a = 20
b = 100
c = a + b
d = a.__add__(b)

print(c)
print(d)


class Student:
    def __init__(self, name):
        self.name = name

    # 定义 + 方法
    def __add__(self, other):
        return self.name + other.name

    def __len__(self):
        return len(self.name)


stu1 = Student('zs')
stu2 = Student('ls')

s = stu1 + stu2
print(s)

lst = [11, 22, 33, 44]
print(len(lst), lst.__len__())

print(len(stu1), stu1.__len__())
